Pay station control trunking for mixed service telephone systems



June 30, 1953 c. E. LOMAX 2,644,040

PAY STATION CONTROL TRUNKING FOR MIXED SERVICE TELEPHONE SYSTEMS Original Filed March 5, 1947 LIJ 5 O Q u A 4 A A, JNVENTOR.

g CLARENCE E. LOMAX ".2 f :1 o I 2 N Z W ATTGRNEY Patented June 30, 1953 PAY STATION CONTROL TRUNKING FOR MIXED SERVICE TELEPHONE SYSTEMS Clarence E. Lomax, Chicago, Ill., assignor to Automatic Electric Laboratories, Inc., Chicago, Ill., a corporation of Delaware Original application March 5, 1947, Serial No. I 732,418. Divided and this application July 28, 1949, Serial No. 107,331

The present invention relates in general to telephone systems .and in particular to mixed service telephone systems, and is a division of my prior application filed March 5, 1947, Serial Number 732,418.

The principal object of the invention is to provide an improved paystation trunk circuit arrangement for serving the paystation lines of a telephone system having both paystation and non-paystation lines.

A feature of the invention relates to switching apparatus and circuit arrangements, whereby a line finder-selector link, capable of serving both paystation and non-paystation lines and distinguishing therebetween, automatically switches a subscriber of a paystation line through the paystation control trunk before the subscribed operates his dial. I

' Another feature resides in the provision of a timing mechanism common to a group of paystation control trunks which operates two relays in a trunk in timed sequence to prevent the con trol trunk from falsely operating, thus insuring that the coins will not be collected in response to certain transient conditions such as pulsing or ring back on reverting calls.

A further feature relates to an arrangement in the control trunk which applies a supervisory signal to a control conductor.

Still another feature is the provision of a cam controlled relay in the paystation control trunk which by its operation sends repeated pulses of high voltage back to the subscribers telephone.

Other objects and features of the invention will become apparent upon a further perusal of the specification taken in conjunction with the accompanying drawing in which:

Fig. 1 illustrates the part of an automatic telephone system which is pertinent to the present invention. A represents a linefinder circuit which is substantially the same as the one disclosed in the United States Patent to Lomax et al. No. 2,214,908, September 17, 1940, but modified to include normal post springs and an extra control lead as shown. B represents a selector circuit substantially like the one disclosed in the above mentioned patent but slightly modified to include normal post springs and an auxiliary relay as shown. C is a schematic diagram of a paystation control trunk including an impulse sender T for operating two relays of the control trunk in timed sequence.

Fig. 2 is a selector like B of Fig. l but having an impulse sender P associated with it as an additional modification.

5 Claims. (Cl. 179-6.3)

The operation of Strowger type finders and selectors is well known in the art and hence it is thought sufiicient here to give only cursory explanation of their operation and to deal more thoroughly with the embodiments of the invention which adapt standard finders and selectors for more economical use in mixed service telephone systems. Reference may be had'to the above mentioned patent for a detailed explanation of the finder and selector operations.

As has been stated, one of the objects of the invention is to provide an arrangement whereby a single group of linefinders are enabled to serve both paystation lines and. non-paystation lines. Since a paystation call requires special control equipment to refund or collect the coins, which equipment is not required for non-paystation calls, it is necessary thatthe linefinder be able to discriminate between the two types of service in order to channel all paystation calls through the control equipment. I accomplish this discrimination by the use of normal post springs on the finder shaft and by connecting all paystation completes a circuit to the start relay ill in a well known manner. Relay I 0 is similar to relay RIM! in Fig. 1 of the above mentioned patent. Relay it thus energized bridges the resistance R across the speaking leads -L and +L at contacts H which causes the pulsing relay 30 of the associated selector to be energized in a manner hereinafter described; Relay It also connects ground to the C conductor atcontact l2. The finder now operates in a well known manner to hunt in a vertical direction for the level to which the calling line is connected. When the finder reaches the first level to which paystation lines are connected it will close its normal post springs l3 to connect ground from the C conductor to an extra control lead EC. This ground on the EC] lead will cause the energization of relay 25 the operation of which will be hereinafter described.

The calling line may be connected to this first paystation level in which case the linefinder Will commence hunting in a rotary direction for the calling line, or it may be connected to a higher level in the group of paystation levels in which case the finder will continue in the vertical direction until it reaches the level to which the calling line is connected whereupon it will commence its rotary hunting. When the linefinder finds the calling line, it connects the calling subscriber's line circuit through to the associated selector which in this case is represented by B.

Relay 30 is a pulsing relay substantially the same as R260 in Fig. 2 of the patent of reference. As soon as relay I operates, relay 30 will be energized over the following circuit, from battery, upper winding of relay 30, contact 2l, resistance R, contacts I I, and 25, and lower winding of relay 30 to ground. Relay 3% performs well known functions one of which is to prepare a circuit to a vertical magnet which will energize to step the selector one vertical step at each subsequent deenergization of relay 30. Relay 25 will operate over an obvious circuit when the finder reaches the first level to which paystation lines are connected and closes its normal post springs I3. Relay 25 thus energized opens the energizing circuit of relay 30 at contacts 25 and 21. Relay 38 in restoring closes a circuit to the vertical magnet which operates and steps the selector one vertical step. The selector is also provided with normal post springs 28 which open when the selector reaches the first level. The operation of the normal post springs 28 opens the energizing circuit of relay 25. Relay 25 restores and closes the energizing circuit of relay 30 at contacts 26 and 21. The first level of the selector has paystation control trunks connected to its bank contacts and the selector now hunts in a rotary direction for an idle one of these control trunks. When it finds an idle trunk it switches the speaking leads L and +L and the C conductor through to the idle control trunk by the operation of a relay (not shown) like R210 of the patent of reference. Thus We see that the selector is automatically stepped to its first level in response to a call originating from a paystation telephone before the calling subscriber operates his dial mechanism.

Fig. 2 shows an arrangement similar to the selector B of Fig. 1 but with the addition of an impulse sender P which is a constantly rotating cam, driven by any suitable means and which may be common to a group of selectors. Relays 20 and I5 are similar to relays 36 and 25 respectively of Fig. l. The finder A of Fig. 1 will now be thought of as being associated with the selector of Fig. 2. As soon as relay III of Fig. l operates, relay 20 will operate over the following circuit, from battery, upper winding of relay 20, contact ll, L conductor, resistance R, contact II, +L conductor, contact I 6, and lower winding of relay 20 to ground. The operation of relay 2!! causes the same subsequent operations in the selector as did the operation of relay 30. It is thought sufficient in explaining the present invention to say that the subsequent operations of relay 20 will cause a vertical magnet to be energized which will step the selector one step in a vertical direction for each deenergization of relay 20. Relay I5 will operate over an obvious circuit when the finder reaches the first level in which paystation lines are connected to its bank contacts at which time the finder will close its normal post springs I3. Relay I 5 thus energized opens the original energizing circuit of relay 20 at contacts I6 and i1 and prepares a new energizing circuit for the upper winding of relay 20 at contact I8. Relay 20 will now be under the control of the impulse sender P and since the pulsing circuit is so short satisfactory pulsing will be obtained by using only one winding of relay 2ll. If the impulse sender P is in the position shown at the instant relay I5 operates and opens its contacts I6 and I1, relay 20 will restore and cause the selector to take one vertical step. If cam it happens to be operating its spring contact I9 at the instant relay I5 operates, relay 20 will hold momentarily on its upper winding over the following circuit; from ground, spring contact I9, make before break contact I8, and upper winding of relay 20 to battery. Relay 20 will alternately operate and restore as the cam mechanism P moves under the spring contact I9 thus causing the selector to take a vertical step every time relay 20 restores. The selector will continue to step in a vertical direction until it operates the'normal post springs 22 at a predetermined level in which paystation control trunks, such as C in Fig. 1, are connected to the bank contacts. In operating its normal post springs 22, the selector opens the energizing circuit of relay (5 at the contacts operated by normal posts springs 22. Relay I5 in restoring closes the original energizing circuit of relay 20 which now holds over this circuit. The selector. now

hunts in a rotary direction for an idle control,

trunk and by the operation of a relay (not shown) similar to R210 of the patent of reference, switches the L, +11, and 0 leads through to the idle control trunk when it has been found.

Consider now the operation of this system when a subscriber calling from a non-paystation telephone initiates a call. The operation of the finder A is as hereinbefore described except that in this case the finder level to which the calling line is connected will be lower than.

the lowest level to which paystation lines are connected hence the finder will never operate its normal post springs such as I3. If the normal post springs of the finder are not operated auxiliary relay 25, 01' I5 of Fig. 2, will not operate and the selector will operate in a well known manner under the control of the subscribers dial mechanism to extend a connection through various trunks and automatic switches to the desired telephone. It is evident that the number one has no utility for use as the first digit of a telephone number in an exchange using the selector of Fig. 1 since-this would put a nonpaystation subscriber through a paystation control trunk on the first digit. By the same token an exchange using the selector of Fig. 2 would have a restricted first digit depending upon the selector level at which the selector normal post springs 22 are set to operate.

Referring now to C of Fig. 1 and assuming that a subscriber has initiated a call from a paystation telephone and that the finder and selector (of either Fig. 1 or 2) have operated as has been described to switch the calling subscribers line through to a paystation control trunk such as C, which is disclosed in Fig. 1. Relay 40 is an electro-polarized relay having one winding in series with a speaking lead and the other winding connected between battery and ground which is returned over the right-hand portion of conductor C from the following selector which is permanently associated with the control trunk. Relay 40 will not operate under this condition as its windings are energized in opposition but it will operate should the current through the speaking leads be reversed. Relay operates, when the trunk is seized, over the following circuit: from battery, winding of. relay 55, contact 61 to the left hand portion of conductor C to ground which is connected at the selector of either Fig. 1 or 2. Relay 55 thus energized closes an obvious locking circuit for itself to the right hand portion of conductor C at contact 58, and completes an obvious circuit for relay 60 at the make contacts of armature 51. Relay 60 operates and completes an obvious circuit for relay 55 at contact 6!. Relay 85 operates and connects an auxiliary ground to the left hand portion of conductor C at contact 66, opens the original energizing circuit of relay 55 at contact 67, connects a supervisory tone to the right hand portion of conductor C at contact 58, prepares a circuit for relay at contact 69, and closes a point in the circuit of relay 98 at contact 18. The supervisory tone applied to the C conductor may be used to inform the operator, if the subscriber is calling an operator, that the call is originating from a paystation telephone so that she may perform the necessary functions to refund the coins to the subscriber. The calling subscriber .now calls the desired party in a well known manner by operating his dial mechanism which will operate a selector switch having access to the same trunks as does the selector B and which may be similar'to the selector disclosed in the patent of reference. While the control trunk is described as working into a selector switch, it should be understood that the control trunk could work into any one of a number of various trunks or switches such as, for instance, a reverting call switch or simply an operators position. Two

conditions may now control the future operation of the paystation trunk. (l) The called party answers the call and a conversation takes place. (2) The called party fails to answer and the calling party hangs up.

Assuming now that the first condition is effective. The current flowing through leads -L, +L, and the left hand winding of relay 48 is made to reverse direction by the action of the called party i when he answers the call. This so called reverse battery feature is well known in the art. Since the windings of relay 48 are now energized in an aiding direction relay 48 operates and prepares a circuit for relay 35 at contact 4|. The operation of relay 35 is now under the control of the impulse sender T which is a constantly rotating cam mechanism driven by any suitable means and which may be common to a group of paystation control trunks. the following circuit when cam 96 operates its spring contact 93; from battery, winding of relay 35, contacts 5|, 4|, 3? and spring contact 93 to ground. Relay 35 thus energized prepares a circuit for relay 45 at contact 38, opens its original energizing circuit at contact 31, and at make before break contact 36 completes a locking circuit for itself as follows; from battery, winding of relay 35, contacts 5|, 4 I, and 36 to the grounded right hand portion of conductor C. The cam mechanism T must now make nearly a complete revolution before cam 95 operates its spring contact 92 at which time the lower winding of relay 45 is energized over the following circuit; from battery, lower winding of relay 45, contact 38, and spring contact 92 to ground. The delay in time between the operation of relays 35 and 45 which is determined by the construction of T and its speed of rotation, is such as to prevent both relays 35 and 45 from operating should relay 48 be momentarily operated as the result of certain transient conditions such as pulsing or ring back on reverting calls. Relay 45 thus energized short circuitsthe left hand winding of relay 48 at contact 43, looks its upper winding to the grounded right hand portion of conductor C at contact 41, completes an obvious circuit to the Thus it is seen that the deenergization of relay is given a momentary delay equal to the time that spring contact 92 is operated by cam 95. This momentary delay in the deenergization of relay 35 is to insure that relay locks up over its upper winding before relay 35 opens the energizing circuit of the lower winding at contact 38. Relay 85, in operating, completes an obvious locking circuit to its upper winding at contact 85, and closes a point in a coin collect circuit at contact 91.

No further changes take place until the conversation has been completed and either the calling or the called party releases all switches in the switch train from the paystation control trunk to the called partys line by releasing his line circuit. This release is accomplished by removing ground from the right hand portion of conductor C in a well known manner. The switches between the paystation control trunk and the calling partys line are held up by the ground applied to the left hand portion of conductor C at contact 66. In response to the removal of ground from the right hand portion of conductor C, relays 45 and 55 will restore. Relay 45 in restoring removes the short circuit from the left hand winding of relay 40 at contact 46, closes a point in the energizing circuit of relay 89 at contact 49, and at contact 53 opens the original energizing circuit of relay 85. In restoring, relay 55 opens a point in its locking circuit at contact 56, opens the energizing circuit of relay 68 at the make contact of armature 5'! and completes an obvious circuit for relay T5 at the break contact of armature 51. Relay is a slow to release relay and when it does release 'it merely opens the energizing circuit to slow release relay 85 at contact Bl. We now have a time interval equal to the restoring time of the two slow to release relays 68 and to collect Relay 35 operates over the coins at the paystation by the action of relay 88. Relay 55 now operates over the followingcircuit: from ground, break contacts of armature 51, contacts 69, and winding of relay T5 to battery. Relay [5 thus energized short circuits the speaking leads L and +L at contacts l1 and. 18, short circuits the left-hand .winding of relay 40 at contact 16, and closes a further point in the energizing circuit for relay at contact [9. Relay 80 now operatesover an 1 as is disclosed in Fig. l of the United States patent to Lomax No. 2,226,731 December 31, 1940 to collect the coins at the paystation telephone. It will be noted that this coin mechanism has its magnet insulated from the line by a glow discharge device in the form of a neon tube. This insulation is necessary to keep ground from the speaking leads so that the pulsing relays 38, or 29, will operate satisfactorily. Relay 89 will continue to pulse under the control of cam .94 until slow to release relay .35 restores at which time relay 85 opens the energizing circuit of relay at contacts 69, opens the energizing circuit of relay 80 at contact H1, and at contact 66 removes ground from the left hand portion of conductor C which in turn releases the preceding switch train. All relays in the paystation control trunk have now restored and the system is ready to receive another call.

Assuming now that the second condition is eifective, namely that the called party fails to answer the call and the calling party hangs up. Relay 40, and consequently relays 35 and 45, cannot operate under this condition in response to reverse battery as that is had only when the called party answers the call. Relays 35 and 45 are prevented from both operating by the delay in the sequence of their operation, which is imparted to them by the cam mechanism T, even should relay 40 operate due to some transient condition such as pulsing or ring back on reverting calls. Relays 55, B0, and 65 are in an operated position as hasbeen hereinbefore described. When the calling subscriber opens his subscribers loop circuit he releases all switches in the switch train except the switches between the calling subscribers line and the paystation control trunk which are held up by the ground applied to the left hand portion of conductor C at contact 66. The restoring of the switch train following the paystation control trunk causes ground to be removed from the right hand portion of conductor C hence the locking circuit for relay 55 is opened and it restores. Relay 55 in restoring opens the energizing circuit of slow to release relay 60 at the make contacts of armature 51 and at the break contacts of armature 51 completes an obvious circuit to relay 15 which now operates. As Was the case under the first condition we now have a time interval equal to the restoring time of the two slow to release relays 6i and 65, in which to operate the coin mechanism at the paystation telephone. Relay 15 in operating short circuits the speaking leads L and +L at contacts H and 13, short circuits the left hand winding of relay 40 at contact 16 and closes a point in the energizing circuit of relay 80 at contact 19. Relay 80 now operates under the control of cam 94 in the same manner as it did under the first condition. Under the present conditionrelay 45 never operates hence relay 85 cannot operate. Relay 85 being held inoperative causes relay 80 to put negative 110 volts from contact 81 through contact 84 onto the short circuited speaking leads L and +L. The negative potential of 110 volts on both sides of the subscriber's line causes the aforementioned coin mechanism to refund the coins to the calling subscriber since his call was not completed. Relay 80, as before, puts several pulses of high voltage on the speaking leads to insure that the coin mechanism refunds the coins. Slow to release relay Biwill soon restore and perform the same functions as it did under the first condition to prepare the system for another call.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is;

1. In a telephone system having calling and called lines and means for establishing connec- 8. tions therebetween, an answer relay, means for operating said answer relay in response to the called subscriber answering the call, a refund circuit, means rendered effective in response to the operation of said relay in case the call is abandoned before the expiration of a predetermined time period for completing said refund circuit, a coin collect circuit, and means rendered effective in response to the operation of said relay after a predetermined time for completing said coin collect circuit in case the call persists beyond said predetermined time period.

2. A telephone system such as claimed in claim 1, including a common timing device for controlling said predetermined time period' 3. In a telephone system having calling and called subscriber lines and means for establishing connections therebetween, a trunk circuit common to said lines and including a coin control circuit, relay'timing meanscom'prising a pair of slow-acting relays also included in said trunk circuit, means for including said trunk circuit in a connection, means whereby said lastmentioned means is responsive to the origination of a call by one of said callinglines, control means for operating said relay timing means, means whereby said control means is responsive to said connection, means for releasing said control means, means whereby said last-mentioned means is responsive to the severance of said call, means for initiating the release of said pair of slow-acting relays in said relay timing means, means whereby said last-mentioned means is responsive to the release of said control means, a timing device, and means effective only during the release time of of said relay timing means and intermittently controlled by said timing device for intermittently completing said coin control circuit.

4. In a telephone system having calling and called subscriber lines and means for. establishing connections therebetween, a common trunk circuit including a first relay, a second relay, a call charging relay and a collect circuit, contacts included in said collect circuit and controlled by said second relay, relay timing means comprising a pair of slowacting relays also included in said trunk circuit, means operated when a call is originated from one of said calling lines for including said trunk circuit in a connection, control means for operating said relay timing means, means whereby said control means is responsive to said connection, means for operating said call charging relay, means whereby said last-mentioned means is responsive to the subsequent answering of said call, means for releasing said control means, means whereby said last-mentioned means is responsive to the severance of said call, means for operating said first relay and for initaiting the release of said pair of slowacting relays in said relay timing means, means whereby said last-mentioned means is responsive to the release of said control means, a control circuit for operating said second relay, contacts controlled by said operated first relay for preparing a point in said control circuit, and a timing device controlling said control circuit by intermittently opening and closing said control circuit to intermittently operate said second relay, whereby said intermittent operations of said second relay operate said contacts in said collect circuit to intermittently complete said collect circuit for collecting the deposit on said call only during the release time of said relay timing means.

5. In a telephone system having calling and called subscriber lines and means for establishing connections therebetween, a common trunk circuit including a first relay, a second relay and a refund circuit, contacts included in said refund circuit and controlled by said second relay, relay timing means comprising a pair of slow-acting relays also included in said trunk circuit, means operated when a call is originated from one of said calling lines for including said trunk circuit in a connection, control means for operating said rela timing means, means whereby said control means is responsive to said connection, means for releasing said control means, means whereby said last-mentioned means is responsive to the abandoning of said call by said calling line, means for operating said first relay and for initiating the release of said pair of slowacting relays in said relay timing means, means whereby said last-mentioned means is responsive to the release of said control means, a control circuit for operating said second relay, and a timing device controlling said control circuit by intermittently opening and closing said control circuit to intermittently operate said second relay, whereby said intermittent operations of said second relay operate said contacts in said refund circuit to intermittently complete said refund circuit for refunding the deposit on said call only during the release time of saidrelay timing means.

CLARENCE E. LOMAX.

References Cited in the file of this patent UNITED STATES PATENTS 

